Increased knowledge of vascular function during chronic gingival inflammation is likely to add to the knowledge of the nature of the disease process and of the prognosis for tissue recovery. Although morphological changes in regular vascular networks to a "looped" arrangement have been demonstrated in free gingiva early in the course of chronic gingivitis, the extent to which changes in vascular function accompany these changes in vascular morphology is not known. The objectives of this research are to investigate selected aspects of vascular function in young and adult non-inflamed and inflamed gingiva of dogs and to induce, under controlled conditions, vascular loop formation in a model vessel network in chick embryo cultures. Blood flow velocity will be measured in specified vessels in vivo and vascular surface area/mm3 subsequently calculated for these vessels from in vitro measurements. Measurements will be made of pO2 gradients from the vascular bed to the epithelial barrier, using vital microscopy and micro-electrodes.